Method for observing biological species

Abstract

A method for observing biological species on a culture medium contained in a container having at least one translucent face, the method including the steps of: a) directing a light beam onto one portion of the translucent face, so as to define at least one illuminated region and at least one non-illuminated region of the face; and b) acquiring an image of a portion of the surface of the culture medium illuminated by the light beam, the acquisition being carried out through at least one of the non-illuminated regions of the translucent face and along an optical acquisition axis forming a non-zero angle (a) with the direction of propagation of the light beam.

The invention claimed is: 
     
       1. A process for observing biological species on a culture medium contained in a container having at least one translucent face, the process comprising the steps:
 a) directing a light beam onto one portion of said translucent face, so as to define at least one illuminated region and at least one non-illuminated region of said face; and 
 b) acquiring an image of a portion of the surface of said culture medium illuminated by said light beam, the acquisition being carried out through said or at least one said non-illuminated region of said translucent face and along an optical acquisition axis forming an angle (α) greater than or equal to 10° with the direction of propagation of said light beam. 
 
     
     
       2. The process as claimed in  claim 1 , wherein steps a) and b) are carried out a plurality of times by defining different illuminated and non-illuminated regions of said translucent face, the process also comprising a step c) of combining the images thus acquired so as to form a combined image. 
     
     
       3. The process as claimed in  claim 2 , wherein said combined image is obtained by combining said acquired images in such a way that, at each point (x,y) of the surface of the culture medium, the acquired image presenting the weakest light intensity measured at said point is selected. 
     
     
       4. The process as claimed in  claim 2 , wherein said combined image is obtained by defining a region of interest of each acquired image, said regions of interest then being combined so as to form the combined image. 
     
     
       5. The process as claimed in  claim 1 , also comprising a step d) consisting of detecting said biological species by discrimination, on said image or combined image, of light or dark regions. 
     
     
       6. The process as claimed in  claim 1 , wherein said light beam defines, on said translucent face, an illuminated region (M 1 ) in the shape of a line. 
     
     
       7. The process as claimed in  claim 1 , wherein said optical acquisition axis does not coincide with the direction of specular reflection of said light beam by said culture medium, as a result of which said biological species appear as light regions on said image. 
     
     
       8. The process as claimed in  claim 1 , wherein said optical acquisition axis coincides approximately with the direction of specular reflection of said light beam by said culture medium, as a result of which said biological species appear as dark regions on said image. 
     
     
       9. The process as claimed in  claim 1 , wherein said face is made translucent by a deposit of scattering material. 
     
     
       10. The process as claimed in  claim 9 , wherein said container is a Petri dish and said translucent face is a lid-of said dish, the internal surface of which is covered with condensation. 
     
     
       11. The process as claimed in  claim 1 , wherein said optical acquisition axis forms an angle between 30° and 60° with said translucent face. 
     
     
       12. The process as claimed in  claim 1 , wherein said face is made translucent by a deposit of scattering material comprised of droplets of condensation.